When an internal combustion engine is running, components of each of friction pairs (such as a crankshaft journal and a bearing; a camshaft journal and a bearing; a piston ring and a cylinder liner) move with respect to each other at a high speed, and a friction loss occurs in the process of their relative movement. The friction between surfaces of each of the friction pairs not only increases power consumption inside the internal combustion engine but also results in a rapid wear of working surfaces of the components, and heat generated in the friction process may also melt surfaces of some working parts, which causes the internal combustion engine to fail to run normally. Therefore, in order to ensure the normal operation of the internal combustion engine, the surfaces of each of the friction pairs in the internal combustion engine must be lubricated.
Currently, a common lubrication of the friction pairs of the internal combustion engine is to pump a lubricating oil with a certain pressure to a clearance between the friction surfaces of each of the friction pairs by an engine oil pump, to form an oil film which has a certain thickness and will not be ruptured when subjected to a certain mechanical load, thereby completely separating the two components of the friction pair from each other as far as possible, and achieving the lubrication effect.
However, taking the friction pair formed by a piston ring and a cylinder liner as an example, in the working process of the internal combustion engine, a hard and large particle is generally presented in a clearance between the piston ring and the cylinder liner, and the large particle may pierce through the oil film. When the piston ring and the cylinder liner move with respect to each other in a vertical direction, the clearance between the piston ring and the cylinder liner is often zero under the action of a bearing force, which results in that the large particle is subjected to an impact and acts on the piston ring or the cylinder liner. Due to the high hardness of the large particle, when the large particle impacts on the friction pair, smooth surfaces of the piston ring and the cylinder liner may form a protrusion-type plastic deformation, for example, a burr and the like. The presence of the burr further incurs a “Fe—Fe dry friction” between the two components of the friction pair.
The “Fe—Fe dry friction” between the two components of the friction pair results in an accelerated wear between the piston ring and the cylinder liner, a shortened service life of the internal combustion engine, and an increased load and an increased fuel consumption of the internal combustion engine, and an exacerbated pollution of the internal combustion engine. Therefore, the reason of wear of the internal combustion engine is the protrusion-type plastic deformations formed on the surfaces of the components of the friction pairs caused by large particles.
In view of the defects in the above lubrication structure of the friction pairs of the internal combustion engine, it is urgent to provide a lubrication structure of an internal combustion engine, to prevent a large particle between components of a friction pair from causing a protrusion-type plastic deformation of surfaces of the components of the friction pair when the large particle is subjected to an impact.